Understanding Mathematics by Peter Alfeld, Department of Mathematics, University of Utah

A simple Logarithm Calculator.

Clicking on this applet

However, your browser does not support Java. If it did you would not see this message! Get a java compatible browser such as Netscape, of a sufficiently advanced version.

will bring up a separate applet that looks much like . That applet lets you pick 2 parameters in the equation

 bx = y.      (*)

and computes the appropriate third value. If you don't understand the equation read this.

The remainder of this page explains how to use the Log machine. The three red text windows contain the numbers y, x, and b, in that sequence. You should read them from the bottom to the top: b to the power x equals y. So in the start up mode we see the equation

23 = 8.

To solve (*) for one variable we need to specify one other and keep the third constant. The yellow buttons in the rightmost column select which variable is kept constant. Clicking on a blank button will cause it to say " constant" and blank the others.

The numbers in the red windows can be changed by highlighting one (or a portion of one) and typing a replacement string. For the change to become effective the "Enter " key must be pressed. An attempt to enter an illegal number (for example a negative value for the base) results in no change. For simplicity, each of the numbers can be incremented or decremented by one (if that's legal) by clicking on the green "+" or "- " buttons, respectively. Any change of a variable causes the other free variable to change correspondingly, so that the equation (*) remains valid. Changing a variable labeled as "constant" causes another one to be kept constant.

The menus next to the "constant" switches let you choose some particular (legal) values for the parameters. Click on them and see what happens!

Clicking on the Quit button will dismiss the calculator. Typing an "x" or a "q" with the cursor in the applet or the calculator window itself will have the same effect.

The run number in the bottom line, if present, indicates how often the program has been run with a working counter since June 27, 1997.

Downloading the Code

You can use the applet without a browser after downloading these two binary files:

These two (binary) files will look strange in your browser, but you should be able to download them using the usual procedure for your browser.

It depends on your system how you invoke a Java bytecode. On my Unix system you can bring up the applet by giving the command

java Log

while connected to the directory that contains the two files mentioned above.

If you have any problems, questions, or comments, please let me know.

Fine print, your comments, more links, Peter Alfeld, PA1UM